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DAC38J84: Fuse farm load completion and errors codes

Larry Flowers
Prodigy 30 points
Part Number: DAC38J84

In our scripts for initial programming of the DAC38J84 we have added a sif_reset (bit 0 of register 0x2) followed by reading memin_efc_autoload (bit 15 of register 0x7f) to verify if the dac is ready for programming.

 

What we have noticed is that once in a while the fuse farm auto load will not complete (bit 15 of register 0x7f not set) and that other times it will complete (bit 15 of register 0x7f set) but with and error code 0x3 in memin_efc_ error (bits 14:10 of register 0x7f).

 

Is there a specific wait time required for the fuse farm load to complete?

 

What does the error code 0x3 in memin_efc_ error indicate?  We do not see this preventing us from programming the registers.

 

If our initial programming includes registers 0x1a and 0x31 (the only registers indicated in the data sheet with a bit that is Fuse Controlled) do we care if either the fuse farm load complete or fuse farm error code does not return the expected value?

  • 0
    TI__Genius 9695 points
    Hi Larry,

    If you are having problems with DAC fusefarm autoload, please check that TRSTB pin of the JTAG interface is grounded. See section 8.3 of datasheet for more details.

    Thanks,
    Eben.
  • 0 in reply to Ebenezer Dwobeng
    Prodigy 30 points
    TRSTB is held low with a 1K ohm resistor. The leakage current from TRSTB seems to be quite a bit higher that the data sheet 40uA as I am getting 98mV across this 1K ohm resistor.
  • 0 in reply to Larry Flowers
    TI__Genius 9695 points
    Hi Larry,

    The information loaded from the fuse farm trims the internal voltages for optimal performance. When using the internal PLL, you may experience PLL lock issues if the fuse farm does not complete or completes with errors.

    If possible please use a lower resistance like 100ohms to pull down the TRSTB pin.

    The fusefarm does require some time to load and it is recommended that you poll the autoload done bit and make sure it is high and there are no errors with fusefarm autoload before proceeding with the rest of the register configuration.

    Thanks,
    Eben.
  • 0 in reply to Ebenezer Dwobeng
    Prodigy 30 points

    Hi Eben,

    I installed a 0 ohm resistor for the TRSTB pull down and still get fuse farm load errors. What else could be causing this?  What clock is being used for fuse farm loading?

    I am not using the internal PLL for DAC clock.

    Thanks

    Larry